Doctors very rarely help those who are terminally ill to die, and two in three oppose changing the law to allow them to do so, research reveals today.

In only one in 200 deaths have doctors given a drug with the explicit intention of speeding death, according to a survey by Clive Seale from Queen Mary University of London, which updates work in 2004.

Where doctors help a patient escape pain or distress, most say they have not shortened life by more than 24 hours and nine out of 10 say their actions hastened death by less than a week. Doctors who admit to it say they had the full collaboration of the patient and family.

The journal Palliative Medicine also publishes a study of the 4,000 doctors' attitudes to euthanasia; 34% are in favour of legalisation and 35% in favour of assisted suicide. That contrasts with 82% and 62% respectively of the public questioned by the survey. The difference is important, says Seale, because governments which enable assisted dying do so only with the support of the profession, as in the Netherlands.

Pressure on the government to act intensified last week when former health secretary Patricia Hewitt called for a change so people need not go to Switzerland to die and put families at risk of prosecution.

Cases where doctors say they give analgesic drugs they know shorten life have dropped from 2004 - to 17.1% from 32.8%. Instances of treatment that might keep people alive longer being withdrawn were also down from 30.3% to 21.8%. This is thought to be partly a result of doctors being asked specifically whether in those cases they intended to end life, as opposed to understanding it was likely to happen.

The survey finds, however, that in 16.5% of cases doctors used continuous deep sedation which can result in the patient effectively being in a coma. In the Netherlands doctors in 2005 said they employed such sedation in 8.5% of cases; in Belgium in 2001 the figure was 8.3%.

"This [disparity] may be a cause for concern if interpretations of this as 'slow euthanasia' are to be avoided," says the survey paper.